Bonded niobium silicide and molybdenum silicide composite articles using brazes

ABSTRACT

An article, such as an airfoil having a melting temperature of at least about 1500° C. and comprising a first piece and a second piece joined by a braze to the first piece. The first piece comprises one of a first niobium-based refractory metal intermetallic composite and a first molybdenum-based refractory metal intermetallic composite, and the second piece comprises one of a second niobium-based refractory metal intermetallic composite and a second molybdenum-based refractory metal intermetallic composite. The braze joining the first piece to the second piece comprises a first metallic element and a second metallic element, wherein the first metallic element is one of titanium, palladium, zirconium, niobium, and hafnium, and wherein the second metallic element is one of titanium, palladium, zirconium, niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron, nickel, and cobalt, the first metallic element being different from the second metallic element. This abstract is submitted in compliance with 37 C.F.R. 1.72( b ) with the understanding that it will not be used to interpret or limit the scope of or meaning of the claims.

BACKGROUND OF THE INVENTION

This application generally relates to composite articles that are joinedtogether using brazes. More particularly, the invention described hereinrelates to bonded niobium-based silicide and molybdenum-based silicidecomposite articles that are joined together using brazes.

Nickel (Ni)-based superalloys have been used as jet engine materials formany years. The surface temperatures at the hottest locations ofstate-of-the-art jet engine turbine airfoils now approach 1,150° C.,which is approximately 85% of the melting temperatures of Ni-basedsuperalloys. Niobium (Nb) and molybdenum (Mo) based refractory metalintermetallic composites (hereinafter referred to as “Nb-based RMICs”and “Mo-based RMICs,”) have much higher potential applicationtemperatures, provided that they can be used at approximately 80% ormore of their melting temperatures, which are generally greater thanabout 1700° C.

Complex silicide-based RMICs that are made from Nb—Si—Ti—Hf—Cr—Al alloysor Mo—Si—B—Cr alloys appear to have the potential to become the nextgeneration turbine materials with a long term, high-temperaturecapability that is significantly higher than that of current Ni-basedsuperalloys. Because of their high melting temperatures, however, directcasting of hollow engine components with cooling channels from these Nb-and Mo-based RMICs is expected to be very difficult. At such hightemperatures, very few materials can serve as casting cores and moldswithout experiencing creep, cracking, or reactions with the moltenmetals and thus contaminating the melt and degrading the cores. Onepotential alternative technique for the manufacture of complex-shapedcomponents (e.g. airfoils) with cooling channels is to bond together,typically using brazes, two or more structural members that have beenmachined to the appropriate shapes. Currently, however, no such brazematerials exist for these Nb- and Mo-based RMICs.

It is known in the art to make hollow components, such as turbineblades, by joining and bonding halves or multiple pieces together.However, the prior-art braze materials that have been developed forNi-based or Fe-based alloys are not suitable for use with the new Nb-and Mo-based RMICs, which have very different alloy compositions andmuch higher working temperatures. Detrimental interactions are known tooccur between nickel brazes, for example, and Nb-based RMICs.

Accordingly, there is a need in the art for improved high temperaturecomposite articles that are joined together using brazes.

BRIEF SUMMARY OF THE INVENTION

The present invention meets this and other needs by providing articlesformed from Nb- and Mo-based RMICs that are joined together by a braze.Brazes for joining Nb- and Mo-based RMICs are also disclosed.

Accordingly, one aspect of the invention is to provide an article havinga melting temperature of at least about 1500° C. The article comprises afirst piece and a second piece joined by a braze to the first piece. Thefirst piece comprises one of a first Nb-based RMIC and a first Mo-basedRMIC, wherein the first Nb-based RMIC comprises titanium, hafnium,silicon, chromium, and niobium, and the first Mo-based RMIC comprisesmolybdenum, silicon, and at least one of chromium and boron. The secondpiece comprises one of a second Nb-based RMIC and a second Mo-basedRMIC, wherein the second Nb-based RMIC comprises titanium, hafnium,silicon, chromium, and niobium, and the second Mo-based RMIC comprisesmolybdenum, silicon, and at least one of chromium and boron.

A second aspect of the invention is to provide an airfoil having amelting temperature of at least about 1500° C. The airfoil comprises afirst piece and a second piece joined by a braze to the first piece. Thefirst piece comprises one of a first Nb-based RMIC and a first Mo-basedRMIC, wherein the Nb-based RMIC comprises titanium, hafnium, silicon,chromium, and niobium, and the first Mo-based RMIC comprises molybdenum,silicon, and at least one of chromium and boron. The second piececomprises one of a second Nb-based RMIC and a second Mo-based RMIC,wherein said second Nb-based RMIC comprises titanium, hafnium, silicon,chromium, and niobium, and the second Mo-based RMIC comprisesmolybdenum, silicon, and at least one of chromium and boron.

A third aspect of the invention is to provide an airfoil having amelting temperature of at least about 1500° C. and comprising a firstpiece and a second piece joined by a braze to the first piece. The firstpiece comprises one of a first Nb-based RMIC and a first Mo-based RMIC,wherein the Nb-based RMIC comprises titanium, hafnium, silicon,chromium, and niobium, and the first Mo-based RMIC comprises molybdenum,silicon, and at least one of chromium and boron. The second piececomprises one of a second Nb-based RMIC and a second Mo-based RMIC,wherein the second Nb-based RMIC comprises titanium, hafnium, silicon,chromium, and niobium, and the second Mo-based RMIC comprisesmolybdenum, silicon, and at least one of chromium and boron. The brazejoining the first piece to the second piece comprises a first metallicelement and a second metallic element, wherein the first metallicelement is one of titanium, palladium, zirconium, niobium, and hafnium,the second metallic element is one of titanium, palladium, zirconium,niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron,nickel, and cobalt, and wherein the first metallic element is differentfrom the second metallic element.

A fourth aspect of the invention is to provide a turbine assembly havingat least one component. The at least one component has a meltingtemperature of at least about 1500° C. and comprises a first piece and asecond piece joined by a braze to the first piece. The first piececomprises one of a first Nb-based RMIC and a first Mo-based RMIC,wherein the Nb-based RMIC comprises titanium, hafnium, silicon,chromium, and niobium, and the first Mo-based RMIC comprises molybdenum,silicon, and at least one of chromium and boron. The second piececomprises one of a second Nb-based RMIC and a second Mo-based RMIC,wherein the second Nb-based RMIC comprises titanium, hafnium, silicon,chromium, and niobium, and the second Mo-based RMIC comprisesmolybdenum, silicon, and at least one of chromium and boron. The brazejoining the first piece to the second piece comprises a first metallicelement and a second metallic element, wherein the first metallicelement is one of titanium, palladium, zirconium, niobium, and hafnium,the second metallic element is one of titanium, palladium, zirconium,niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron,nickel, and cobalt, and wherein the first metallic element is differentfrom the second metallic element.

Finally, a fifth aspect of the invention is to provide a method ofmaking an article having a melting temperature of at least about 1500°C. and comprising a first piece and a second piece that are joinedtogether by a braze. The first piece and second piece each comprise oneof a niobium based refractory intermetallic composite and a molybdenumsilicide based composite, wherein the niobium based refractoryintermetallic composite comprises titanium, hafnium, silicon, chromium,and niobium and the molybdenum silicide based composite comprisesmolybdenum, silicon, and at least one of chromium and boron. The methodcomprises the steps of: providing the first piece and the second piecesuch that the first piece and the second piece form a an interfacetherebetween; providing a braze to the interface between the first pieceand the second piece, the braze having a melting temperature andcomprising a first metallic element and a second metallic element, thefirst metallic element one of titanium, palladium, zirconium, niobium,and hafnium, and the second metal one of titanium, palladium, zirconium,niobium, hafnium, aluminum, chromium, vanadium, platinum, gold, iron,nickel, and cobalt, wherein the first metallic element is different fromthe second metallic element; heating the first piece, the second piece,and the braze to a first temperature for a first predetermined holdtime, the first temperature being at least about 20° C. above themelting temperature of the braze; and further heating the first piece,the second piece, and the braze to a temperature up to about 1450° C.for a second predetermined hold time, thereby joining the first pieceand the second piece at the interface and forming the article.

These and other aspects, advantages, and salient features of the presentinvention will become apparent from the following detailed description,the accompanying drawings, and the appended claims.

LIST OF FIGURES

FIG. 1 is a schematic illustration of a brazed article in accordancewith one embodiment of the present invention;

FIG. 2 is a plot of approximate temperature regimes of the brazing andhomogenization operations relative to the melting temperatures and thepotential working temperatures of Nb- and Mo-based RIMCs; and

FIG. 3 is a method flow chart in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that terms such as “top,” “bottom,”“outward,” “inward,” and the like are words of convenience and are notto be construed as limiting terms.

Referring to the drawings in general and to FIG. 1 in particular, itwill be understood that the illustrations are for the purpose ofdescribing a preferred embodiment of the invention and are not intendedto limit the invention thereto.

An article 10, such as an airfoil, that is adapted for exposure tohigh-temperature conditions, typically greater than about 1000° C.,includes a first piece 12 and a second piece 14, as shown in FIG. 1. Inan exemplary embodiment, article 10 is an airfoil, for example adouble-walled airfoil, for use within a hot gas path of a turbineassembly. Article 10 may be a component, such as a diffuser, casing,seal ring structure, or the like that is intended for use in a turbineassembly or any other structure in which temperatures in excess of about1000° C. are encountered. Article 10 has a melting temperature of atleast about 1500° C. Preferably, article 10 has a melting temperature ofat least about 1700° C.

First piece 12 is made of a first niobium based refractory metalintermetallic composite (hereinafter referred to as “Nb-based RMIC”) ora first molybdenum silicide based refractory metal intermetalliccomposite (hereinafter referred to as “Mo-based RMIC”). The firstNb-based RMIC typically comprises titanium, hafnium, silicon, chromium,and niobium and first Mo-based RMIC typically comprises molybdenum,silicon, and at least one of chromium and boron.

Second piece 14 is joined by a braze 16 to first piece 12. Second piece14 is made of a second Nb-based RMIC or a second Mo-based RMIC. Thesecond Nb-based RMIC typically comprises titanium, hafnium, silicon,chromium, and niobium, and the second Mo-based RMIC typically comprisesmolybdenum, silicon, and at least one of chromium and boron.

The Nb-based RMICs that are used to form the article 10 of the presentinvention possess a good balance of oxidation resistance and mechanicalproperties. The Nb-based RMICs preferably have compositions in the rangeof: between about 20 and about 30 atomic percent titanium; between about13 and about 20 atomic percent silicon; between about 2 and about 10atomic percent hafnium; between about 1 and about 12 atomic percentchromium; between about 1 and about 3 atomic percent aluminum; andbetween about 5 and about 7 atomic percent boron; with the balancecomprising niobium. In order to provide even greater oxidationresistance, these alloys may optionally contain greater amounts ofchromium and aluminum. In addition, the Nb-based RMICs may furtherinclude up to about 4 atomic percent Ge, and up to about 6 atomicpercent each of Mo, Ta, V, W, Fe, Sn, and Zr.

In the present invention, the Mo-based RMICs that are used to form thearticle 10 are based on molybdenum silicides, such as, but not limitedto, MoSi₂, Mo₃Si, Mo₅Si₃, and Mo₅SiB₂ and comprise molybdenum, silicon,and at least one of boron or chromium. The Mo-based RMICs preferablycomprise between about 2.5 and about 13.5 atomic percent silicon,between about 3.5 and about 26.5 atomic percent boron, and a balance ofmolybdenum. Alternatively, the Mo-based RMICs may comprise between about13 and about 16 atomic percent silicon, between about 25 and about 40atomic percent chromium, and a balance of molybdenum. The Mo-based RMICsmay also include other elements, such as, but not limited to, tantalum,titanium, zirconium, rhenium, carbon, hafnium, germanium, tungsten,vanadium, tin, and aluminum.

The joints formed by braze 16 at interface 18 in article 10 must sustainthermal, axial/centrifugal, and pressure differential stresses. In anairfoil, for example, the gas path side of the article (formed by secondpiece 14 in FIG. 1) may experience temperatures of about 1315° C.,whereas the cold side (formed by first piece 12 in FIG. 1) may onlyreach about 1000° C. Both steady-state and transient (during aircrafttakeoffs and landings) thermal stresses thermal stresses act upon thebonding surfaces in shear mode. The pressure differential between thegas path side and the cold side can be as high as about 0.1 ksi, and itwill exert ballooning, or tensile, stresses on the bonding surfaces atinterface 18. In addition, the airfoils also produce centrifugalstresses during rotation that act upon the bonding surface in a shearmode. The combined stresses acting on the bonding surfaces can be verysignificant at the potentially high operating temperatures of a turbineassembly. The joints formed by braze 16 at interface 18 must sustainsuch stresses.

The interaction between braze 16, first piece 12, and second piece 14must also be considered. The braze 16 must not significantly degrade theproperties of the Nb- and/or Mo-based RMICs that form first piece 12 andsecond piece 14; it is preferable that braze 16 consume as little offirst piece 12 and/or second piece 14 as is practical. Moreover, thebraze 16 must have enough oxidation and environmental resistance toavoid internal oxidation during the brazing and subsequenthomogenization processes.

Temperature regimes for the bonding operations also impose constraintson selection of braze 16 for joining first piece 12 and second piece 14.Preferably, braze 16 can be used for joining first piece 12 and secondpiece 14 at temperatures lower than about 1450° C. Bonding of firstpiece 12 and second piece 14 at temperatures higher than about 1450° C.requires expensive tooling and fixtures that may not be able to producearticle 10 having the required precision in dimensions. In addition,internal oxidation becomes a severe threat to a good bonding at highertemperatures. On the other hand, when the braze 16 has a meltingtemperature below the potential operating temperatures (e.g., about1000° C.) of article 10, care must be taken to ensure that low eutecticcompositions of braze 16 with either first piece 12 or second piece 14do not exist after homogenization of the interface.

Interdiffusion of elements from the braze 16 into first piece 12 andsecond piece 14 enhances joining of first piece 12 and second piece 14by braze 16. Thus, the solubility of the elements of braze 16 in theNb-based and/or Mo-based RIMCs must also be taken into account. Afterbrazing and homogenization, the bonded and diffused regions of article10 preferably have melting temperatures of up to about 1450° C. Inservice, joints formed by braze 16 at interface 18 in article 10 areexposed to temperatures that are close to the bulk temperature ofarticle 10, or up to about 1200° C., rather than the temperature of upto about 1315° C. that is experienced by the surface (formed by secondpiece 14 in FIG. 1) of article 10. The approximate temperature regimesof the brazing and homogenization operations relative to the meltingtemperatures and the potential working temperatures of Nb- and Mo-basedRIMCs are summarized in FIG. 2.

Braze 16 is typically made of first metal and a second metal. The firstmetal is a metallic element selected from one of titanium, palladium,zirconium, niobium, and hafnium. The second metallic element is one oftitanium, palladium, zirconium, niobium, hafnium, aluminum, chromium,vanadium, platinum, gold, iron, nickel, and cobalt. Although elementssuch as palladium, platinum, gold, zirconium, iron, nickel, cobalt, andthe like are not components of the Nb- and Mo-based RMICs, theseelements have good solubility in the metal bcc phase, and thus promoteformation of the metal phase, which in turn enhances braze jointductility and toughness.

In a first embodiment, braze 16 comprises between about 30 to about 90atomic percent titanium with the balance comprising a metal selectedfrom the group consisting of palladium, platinum, gold, chromium,cobalt, nickel, and iron. Braze 16 may further include at least oneadditional element selected from the group consisting of silicon,germanium, hafnium, niobium, palladium, platinum, gold, aluminum,chromium, boron, zirconium, iron, cobalt, nickel, and vanadium, whereinthe at least one additional element comprises up to 20 atomic percent ofbraze 16. The at least one additional element is different from thefirst metallic element and second metallic element.

In one preferred embodiment, braze 16 comprises between about 90 andabout 55 atomic percent titanium with the balance comprising palladium.More preferably, braze 16 comprises between about 63 and about 73 atomicpercent titanium with the balance comprising palladium.

In another preferred embodiment, braze 16 comprises between about 80 andabout 30 atomic percent titanium with the balance comprising chromium.More preferably, braze 16 comprises between about 50 and about 60 atomicpercent titanium with the balance comprising chromium.

In another preferred embodiment, braze 16 comprises between about 94 andabout 74 atomic percent titanium with the balance comprising platinum.More preferably, braze 16 comprises between about 82 and about 86 atomicpercent titanium with the balance comprising platinum.

In another preferred embodiment, braze 16 comprises between about 99 andabout 59 atomic percent titanium with the balance comprising platinum.More preferably, braze 16 comprises between about 74 and about 84 atomicpercent titanium with the balance comprising gold.

In another preferred embodiment, braze 16 comprises between about 58 andabout 90 atomic percent titanium with the balance comprising cobalt.More preferably, braze 16 comprises between about 68 and about 78 atomicpercent titanium with the balance comprising cobalt.

In another preferred embodiment, braze 16 comprises between about 90 andabout 50 atomic percent titanium with the balance comprising cobalt.More preferably, braze 16 comprises between about 70 and about 80 atomicpercent titanium with the balance comprising iron.

In another preferred embodiment, braze 16 comprises between about 50 andabout 90 atomic percent titanium with the balance comprising nickel.More preferably, braze 16 comprises between about 71 and about 81 atomicpercent titanium with the balance comprising nickel.

In a second embodiment, braze 16 comprises between about 20 and about 85atomic percent palladium with the balance comprising one of chromium,aluminum, hafnium, zirconium, niobium, and vanadium. Braze 16 mayfurther include at least one additional element selected from the groupconsisting of silicon, germanium, hafnium, niobium, platinum, gold,aluminum, chromium, boron, zirconium, titanium, iron, nickel, cobalt,and vanadium, wherein the at least one additional element comprises upto 20 atomic percent of braze 16. The at least one additional element isdifferent from the first metallic element and second metallic element.

In a preferred embodiment, braze 16 comprises between about 20 and about80 atomic percent palladium with the balance comprising chromium. Morepreferably, braze 16 comprises between about 39 and about 49 atomicpercent palladium with the balance comprising chromium.

In another preferred embodiment, braze 16 comprises between about 70 andabout 86 atomic percent palladium with the balance comprising aluminum.More preferably, braze 16 comprises between about 75 and about 81 atomicpercent palladium with the balance comprising aluminum.

In another preferred embodiment, braze 16 comprises between about 22 andabout 32 atomic percent palladium with the balance comprising hafnium.More preferably, braze 16 comprises between about 25 and about 29 atomicpercent palladium with the balance comprising hafnium.

In another preferred embodiment, braze 16 comprises between about 10 andabout 35 atomic percent palladium with the balance comprising zirconium.More preferably, braze 16 comprises between about 22 and about 28 atomicpercent palladium with the balance comprising zirconium.

In another preferred embodiment, braze 16 comprises between about 35 andabout 60 atomic percent palladium with the balance comprising niobium.More preferably, braze 16 comprises between about 45 and about 49 atomicpercent palladium with the balance comprising niobium.

In another preferred embodiment, braze 16 comprises between about 20 andabout 60 atomic percent palladium with the balance comprising vanadium.More preferably, braze 16 comprises between about 36 and about 44 atomicpercent palladium with the balance comprising vanadium.

In a third embodiment, braze 16 comprises between about 45 and about 90atomic percent zirconium with the balance comprising one of platinum andvanadium. Braze 16 may further include at least one additional elementselected from the group consisting of silicon, germanium, hafnium,niobium, platinum, palladium, gold, aluminum, chromium, boron, titanium,iron, nickel, cobalt, and vanadium, wherein the at least one additionalelement comprises up to 20 atomic percent of braze 16. The at least oneadditional element is different from the first metallic element andsecond metallic element.

In a preferred embodiment, braze 16 comprises between about 68 and about90 atomic percent zirconium with the balance comprising platinum. Morepreferably, braze 16 comprises between about 77 and about 81 atomicpercent zirconium with the balance comprising platinum.

In another preferred embodiment, braze 16 comprises between about 45 andabout 65 atomic percent zirconium with the balance comprising vanadium.More preferably, braze 16 comprises between about 55 and about 59 atomicpercent zirconium with the balance comprising vanadium.

In a fourth embodiment, braze 16 comprises between about 15 and about 80atomic percent niobium with the balance comprising one of iron, nickel,and cobalt. Braze 16 may further include at least one additional elementselected from the group consisting of silicon, germanium, hafnium,palladium, platinum, gold, aluminum, chromium, boron, titanium, iron,nickel, cobalt, and vanadium, wherein the at least one additionalelement comprises up to 20 atomic percent of the first component ofbraze 16. The at least one additional element is different from thefirst metallic element and second metallic element.

In a preferred embodiment, braze 16 comprises between about 50 and about80 atomic percent niobium with the balance comprising iron. Morepreferably, braze 16 comprises between about 62 and about 66 atomicpercent niobium with the balance comprising iron.

In another preferred embodiment, braze 16 comprises between about 15 andabout 50 atomic percent niobium with the balance comprising nickel. Morepreferably, braze 16 comprises between about 35 and about 45 atomicpercent niobium with the balance comprising nickel.

In another preferred embodiment, braze 16 comprises between about 50 andabout 71 atomic percent niobium with the balance comprising cobalt. Morepreferably, braze 16 comprises between about 59 and about 63 atomicpercent niobium with the balance comprising cobalt.

In a fifth embodiment, the first component of braze 16 comprises betweenabout 54 and about 74 atomic percent hafnium with the balance comprisingiron. More preferably, braze 16 comprises between about 62 and about 64atomic percent hafnium with the balance comprising iron. Braze 16 mayfurther include at least one additional element selected from the groupconsisting of palladium, gold, niobium, aluminum, chromium, cobalt,nickel, boron, and vanadium, wherein the at least one additional elementcomprises up to 20 atomic percent of braze 16. The at least oneadditional element is different from the first metallic element andsecond metallic element.

Compositions of braze 16 are summarized in Table 1.

TABLE 1 List of materials for first component of braze for joining Nb—and Mo— based RMICs based on binary metallic systems. Preferred brazeMore composition preferred range, composition at. % range, at. % Furtheradditions, total amount up to 20 at. % Ti: 90-55 Ti: 67.5 ± 5 Ge, Si,Hf, Nb, Pt, Au, Al, Cr, B, Fe, Co, Ni Pd: 10-45 Pd: 32.5 ± 5 Cr: 80-20Cr: 56 ± 5 Ge, Si, Al, Ti, Pt, Nb, Zr, V, Hf, Au, B, Fe, Co, Ni Pd:20-80 Pd: 44 ± 5 V: 55-45 V: 43 ± 2 Ge, Si, Al, Ti, Nb, Cr, Hf, Pt, Pd,Au, B, Fe, Co, Ni Zr: 45-65 Zr: 57 ± 2 Pd: 70-86 Pd: 78 ± 3 Ge, Si, Ti,Nb, Cr, Zr, V, Hf, Pt, Au, B, Fe, Co, Ni Al: 30-14 Al: 21 ± 3 Ti: 80-30Ti: 55 ± 5 Ge, Si, Al, Nb, Zr, V, Hf, Pt, Pd, Au, B, Fe, Co, Ni Cr:20-70 Cr: 45 ± 5 Ti: 74-94 Ti: 84 ± 2 Ge, Si, Al, Cr, Nb, V, Hf, Pd, Au,B, Fe, Co, Ni Pt: 6-26 Pt: 16 ± 2 Pd: 22-32 Pd: 27 ± 2 Ge, Si, Al, Ti,Cr, Nb, Zr, V, Pt, Au, B, Fe, Co, Ni Hf: 78-68 Hf: 73 ± 2 Pd: 10-35 Pd:25 ± 3 Ge, Si, Al, Ti, Cr, Nb, V, Hf, Pt, Au, B, Fe, Co, Ni Zr: 90-65Zr: 75 ± 3 Pt: 10-32 Pd: 21 ± 2 Ge, Si, Al, Ti, Cr, Nb, V, Hf, Pd, Au,B, Fe, Co, Ni Zr: 90-68 Zr: 79 ± 2 Nb: 65-40 Nb: 53 ± 2 Ge, Si, Al, Ti,Cr, V, Hf, Pt, Au, B, Fe, Co, Ni Pd: 35-60 Pd: 47 ± 2 Pd: 20-60 Pd: 40 ±4 Ge, Si, Al, Ti, Cr, Nb, Zr, Hf, Pt, Au, B, Fe, Co, Ni V: 80-40 V: 60 ±4 Ti: 90-55 Ti: 79 ± 5 Ge, Si, Al, Nb, Cr, V, Hf, Pt, Pd, B, Fe, Co, NiAu: 10-45 Au: 21 ± 5 Ti: 58-90 Ti: 73 ± 5 Ge, Si, Al, Nb, Cr, V, Hf, Pt,Pd, Au, B, Fe, Ni Co: 42-10 Co: 27 ± 5 Ti: 90-50 Ti: 70 ± 5 Ge, Si, Al,Nb, Cr, V, Hf, Pt, Pd, Au, B, Co, Ni Fe: 10-50 Fe: 30 ± 5 Ti: 90-50 Ti:76 ± 5 Ge, Si, Al, Nb, Cr, V, Hf, Pt, Pd, Au, B, Fe, Co Ni: 10-50 Ni: 24± 5 Nb: 80-50 Nb: 64 ± 2 Ge, Si, Al, Ti, Cr, V, Hf, Pt, Pd, Au, B, Co,Ni Fe: 20-50 Fe: 36 ± 2 Nb: 15-50 Nb: 40.5 ± 5 Ge, Si, Al, Ti, Cr, V,Hf, Pd, Au, B, Fe, Co Ni: 85-50 Ni: 59.5 ± 5 Nb: 71-50 Nb: 61 ± 2 Ge,Si, Al, Ti, Cr, V, Hf, Pd, Au, B, Fe, Ni Co: 29-50 Co: 39 ± 2 Hf: 54-74Hf: 64 ± 2 Al, Nb, Cr, V, Pd, Au, B, Co, Ni Fe: 46-26 Fe: 36 ± 2

A method 100 of making article 10 is shown in FIG. 2. First, in step S1,first piece 12 and second piece 14 are provided such that first piece 12and second piece 14 form an interface 18 therebetween. Next, in step S2,braze 16 is provided to interface 18 between first piece 12 and secondpiece 14. Braze 16 may be provided to interface 18 as a foil, which issandwiched between first piece 12 and second piece 14. In thoseinstances where braze 16 is too brittle to be formed into a foil, eithera powder tape or powder paste of braze 16 may be used to provide thebraze 16 to the interface 18. Braze 16 includes a first metal and asecond metal, the first metal is a metal selected from the groupconsisting of titanium, palladium, zirconium, niobium, and hafnium, andthe second metal is a metal selected from the group consisting oftitanium, palladium, zirconium, niobium, hafnium, aluminum, chromium,vanadium, platinum, gold, iron, nickel, and cobalt.

Next, at step S3, first piece 12, second piece 14, and braze 16 areheated to a first temperature for a first predetermined hold time, thefirst temperature being at least 20° C. above the melting temperature ofbraze 16. Next, at step S4, first piece 12, second piece 14, and braze16 are further heated to a temperature up to about 1450° C. for a secondpredetermined hold time, thereby joining first piece 12 and second piece14 at interface 18 and forming article 10.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing description should not be deemed to be alimitation on the scope of the invention. Accordingly, variousmodifications, adaptations, and alternatives may occur to one skilled inthe art without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. An article having a melting temperature of atleast about 1500° C., said article comprising: a) a first piececomprising one of a first niobium-based refractory metal intermetalliccomposite and a first molybdenum-based refractory metal intermetalliccomposite, wherein said first niobium-based refractory metalintermetallic composite comprises titanium, hafnium, silicon, chromium,and niobium, and said first molybdenum-based refractory metalintermetallic composite comprises molybdenum, silicon, and at least oneof chromium and boron; and b) a second piece joined by a braze to saidfirst piece, said second piece comprising one of a second niobium-basedrefractory metal intermetallic composite and a second molybdenum-basedrefractory metal intermetallic composite, wherein said secondniobium-based refractory metal intermetallic composite comprisestitanium, hafnium, silicon, chromium, and niobium, and said secondmolybdenum-based refractory metal intermetallic composite comprisesmolybdenum, silicon, and at least one of chromium and boron, whereinsaid braze comprises a first metallic element and a second metallicelement, wherein said first metallic element is one of titanium,palladium, zirconium, niobium, and hafnium, and wherein said secondmetal is one of titanium, palladium, zirconium, niobium, hafnium,aluminum, chromium, vanadium, platinum, gold, iron, nickel, and cobalt,and wherein said first metallic element is different from said secondmetallic element.
 2. The article according to claim 1, wherein saidbraze comprises between about 30 and about 90 atomic percent titaniumwith the balance comprising one of palladium, platinum, gold, chromium,cobalt, nickel, and iron.
 3. The article according to claim 2, whereinsaid braze further comprises at least one additional element selectedfrom the group consisting of silicon, germanium, hafnium, niobium,palladium, platinum, gold, aluminum, chromium, boron, zirconium, iron,cobalt, nickel, and vanadium, and wherein said at least one additionalelement comprises up to about 20 atomic percent of said braze.
 4. Thearticle according to claim 2, wherein said braze comprises between about90 and about 55 atomic percent titanium and a balance of palladium. 5.The article according to claim 4, wherein said braze comprises betweenabout 63 and about 73 atomic percent titanium and a balance ofpalladium.
 6. The article according to claim 2, wherein said brazecomprises between about 80 and about 30 atomic percent titanium and abalance of chromium.
 7. The article according to claim 6, wherein saidbraze comprises between about 50 and about 60 atomic percent titaniumand a balance of chromium.
 8. The article according to claim 2, whereinsaid braze comprises between about 94 and about 74 atomic percenttitanium and a balance of platinum.
 9. The article according to claim 8,wherein said braze comprises between about 82 and about 86 atomicpercent titanium and a balance of platinum.
 10. The article according toclaim 2, wherein said braze comprises between about 99 and about 59atomic percent titanium and a balance of gold.
 11. The article accordingto claim 10, wherein said braze comprises between about 74 and about 84atomic percent titanium and a balance of gold.
 12. The article accordingto claim 2, wherein said braze comprises between about 58 and about 90atomic percent titanium and a balance of cobalt.
 13. The articleaccording to claim 12, wherein said braze comprises between about 68 andabout 78 atomic percent titanium and a balance of cobalt.
 14. Thearticle according to claim 2, wherein said braze comprises between about90 and about 50 atomic percent titanium and a balance of iron.
 15. Thearticle according to claim 14, wherein said braze comprises betweenabout 70 and about 80 atomic percent titanium and a balance of iron. 16.The article according to claim 2, wherein said braze comprises betweenabout 50 and about 90 atomic percent titanium and a balance of nickel.17. The article according to claim 16, wherein said braze comprisesbetween about 71 and about 81 atomic percent titanium and a balance ofnickel.
 18. The article according to claim 1, wherein said brazecomprises between about 20 and about 85 atomic percent palladium withthe balance comprising one of chromium, aluminum, hafnium, zirconium,niobium, and vanadium.
 19. The article according to claim 18, whereinsaid braze further comprises at least one additional element selectedfrom the group consisting of silicon, germanium, hafnium, niobium,platinum, gold, aluminum, chromium, boron, zirconium, titanium, iron,nickel, cobalt, and vanadium, and wherein said at least one additionalelement comprises up to about 20 atomic percent of said braze.
 20. Thearticle according to claim 18, wherein said braze comprises betweenabout 20 and about 80 atomic percent palladium and a balance ofchromium.
 21. The article according to claim 20, wherein said brazecomprises between about 39 and about 49 atomic percent palladium and abalance of chromium.
 22. The article according to claim 18, wherein saidbraze comprises between about 70 and about 86 atomic percent palladiumand a balance of aluminum.
 23. The article according to claim 22,wherein said braze comprises between about 75 and about 81 atomicpercent palladium and a balance of aluminum.
 24. The article accordingto claim 18, wherein said braze comprises between about 22 and about 32atomic percent palladium and a balance of hafnium.
 25. The articleaccording to claim 24, wherein said braze comprises between about 25 andabout 29 atomic percent palladium and a balance of hafnium.
 26. Thearticle according to claim 18, wherein said braze comprises betweenabout 10 and about 35 atomic percent palladium and a balance ofzirconium.
 27. The article according to claim 26, wherein said brazecomprises between about 22 and about 28 atomic percent palladium and abalance of zirconium.
 28. The article according to claim 18, whereinsaid braze comprises between about 35 and about 60 atomic percentpalladium and a balance of niobium.
 29. The article according to claim28, wherein said braze comprises between about 45 and about 49 atomicpercent palladium and a balance of niobium.
 30. The article according toclaim 18, wherein said braze comprises between about 20 and about 60atomic percent palladium and a balance of vanadium.
 31. The articleaccording to claim 30, wherein said braze comprises between about 36 andabout 44 atomic percent palladium and a balance of vanadium.
 32. Thearticle according to claim 1, wherein said braze comprises between about45 and about 90 atomic percent zirconium with the balance comprising oneof platinum and vanadium.
 33. The article according to claim 32, whereinsaid braze further comprises at least one additional element selectedfrom the group consisting of silicon, germanium, hafnium, niobium,platinum, palladium, gold, aluminum, chromium, boron, titanium, iron,nickel, cobalt, and vanadium, and wherein said at least one additionalelement comprises up to about 20 atomic percent of said braze.
 34. Thearticle according to claim 32, wherein said braze comprises betweenabout 68 and about 90 atomic percent zirconium and a balance ofplatinum.
 35. The article according to claim 34, wherein said brazecomprises between about 77 and about 81 atomic percent zirconium and abalance of platinum.
 36. The article according to claim 32, wherein saidbraze comprises between about 45 and about 65 atomic percent zirconiumand a balance of vanadium.
 37. The article according to claim 36,wherein said braze comprises between about 55 and about 59 atomicpercent zirconium and a balance of vanadium.
 38. The article accordingto claim 1, wherein said braze comprises between about 15 and about 80atomic percent niobium with the balance comprising one of iron, nickel,and cobalt.
 39. The article according to claim 38, wherein said brazefurther comprises at least one additional element selected from thegroup consisting of silicon, germanium, hafnium, palladium, platinum,gold, aluminum, chromium, boron, titanium, iron, nickel, cobalt, andvanadium, and wherein said at least one additional element comprises upto about 20 atomic percent of said braze.
 40. The article according toclaim 38, wherein said braze comprises between about 50 and about 80atomic percent niobium and a balance of iron.
 41. The article accordingto claim 40, wherein said braze comprises between about 62 and about 66atomic percent niobium and a balance of iron.
 42. The article accordingto claim 38, wherein said braze comprises between about 15 and about 50atomic percent niobium and a balance of nickel.
 43. The articleaccording to claim 42, wherein said braze comprises between about 35 andabout 45 atomic percent niobium and a balance of nickel.
 44. The articleaccording to claim 38, wherein said braze comprises between about 50 andabout 71 atomic percent niobium and a balance of cobalt.
 45. The articleaccording to claim 44, wherein said braze comprises between about 59 andabout 63 atomic percent niobium and a balance of cobalt.
 46. The articleaccording to claim 1, wherein said braze comprises between about 54 andabout 74 atomic percent hafnium with the balance comprising iron. 47.The article according to claim 46, wherein said braze further comprisesat least one additional element selected from the group consisting ofpalladium, gold, aluminum, niobium, chromium, cobalt, nickel, boron, andvanadium, and wherein said at least one additional element comprises upto about 20 atomic percent of said braze.
 48. The article according toclaim 46, wherein said braze comprises between about 62 and about 64atomic percent hafnium with the balance comprising iron.
 49. The articleaccording to claim 1, wherein said melting temperature is at least about1700° C.
 50. The article according to claim 1, wherein said first piececomprises said first niobium-based refractory metal intermetalliccomposite.
 51. The article according to claim 50, wherein said secondpiece comprises said second niobium-based refractory metal intermetalliccomposite.
 52. The article according to claim 1, wherein said firstpiece comprises said first molybdenum-based refractory metalintermetallic composite.
 53. The article according to claim 52, whereinsaid second piece comprises said second molybdenum-based refractorymetal intermetallic composite.
 54. The article according to claim 1,wherein said article is one of an airfoil, a diffuser, a casing, and aseal ring structure.
 55. The article according to claim 54, wherein saidarticle has a service temperature of at least about 1000° C.
 56. Anairfoil having a melting temperature of at least about 1500° C., saidairfoil comprising: a) a first piece comprising one of a firstniobium-based refractory metal intermetallic composite and a firstmolybdenum-based refractory metal intermetallic composite, wherein saidfirst niobium-based refractory metal intermetallic composite comprisestitanium, hafnium, silicon, chromium, and niobium, and said firstmolybdenum-based refractory metal intermetallic composite comprisesmolybdenum, silicon, and at least one of chromium and boron; and b) asecond piece joined by a braze to said first piece, said second piececomprising one of a second niobium-based refractory metal intermetalliccomposite and a second molybdenum-based refractory metal intermetalliccomposite, wherein said second niobium-based refractory metalintermetallic composite comprises titanium, hafnium, silicon, chromium,and niobium, and said second molybdenum-based refractory metalintermetallic composite comprises molybdenum, silicon, and at least oneof chromium and boron, and wherein said braze comprises a first metallicelement and a second metallic element, wherein said first metallicelement is one of titanium, palladium, zirconium, niobium, and hafnium,and wherein said second metallic element is one of titanium, palladium,zirconium, niobium, hafnium, aluminum, chromium, vanadium, platinum,gold, iron, nickel, and cobalt, wherein said first metallic element isdifferent from said second metallic element.
 57. The airfoil accordingto claim 56, wherein said braze comprises between about 30 and about 90atomic percent titanium with the balance comprising one of palladium,platinum, gold, chromium, cobalt, nickel, and iron.
 58. The airfoilaccording to claim 57, wherein said braze further comprises at least oneadditional element selected from the group consisting of silicon,germanium, hafnium, niobium, palladium, platinum, gold, aluminum,chromium, boron, zirconium, iron, cobalt, nickel, and vanadium, andwherein said at least one additional element comprises up to about 20atomic percent of said braze.
 59. The airfoil according to claim 57,wherein said braze comprises between about 90 and about 55 atomicpercent titanium and a balance of palladium.
 60. The airfoil accordingto claim 59, wherein said braze comprises between about 63 and about 73atomic percent titanium and a balance of palladium.
 61. The airfoilaccording to claim 57, wherein said braze comprises between about 80 andabout 30 atomic percent titanium and a balance of chromium.
 62. Theairfoil according to claim 61, wherein said braze comprises betweenabout 50 and about 60 atomic percent titanium and a balance of chromium.63. The airfoil according to claim 57, wherein said braze comprisesbetween about 94 and about 74 atomic percent titanium and a balance ofplatinum.
 64. The airfoil according to claim 63, wherein said brazecomprises between about 82 and about 86 atomic percent titanium and abalance of platinum.
 65. The airfoil according to claim 57, wherein saidbraze comprises between about 99 and about 59 atomic percent titaniumand a balance of gold.
 66. The airfoil according to claim 65, whereinsaid braze comprises between about 74 and about 84 atomic percenttitanium and a balance of gold.
 67. The airfoil according to claim 57,wherein said braze comprises between about 58 and about 90 atomicpercent titanium and a balance of cobalt.
 68. The airfoil according toclaim 67, wherein said braze comprises between about 68 and about 78atomic percent titanium and a balance of cobalt.
 69. The airfoilaccording to claim 57, wherein said braze comprises between about 90 andabout 50 atomic percent titanium and a balance of iron.
 70. The airfoilaccording to claim 69, wherein said braze comprises between about 70 andabout 80 atomic percent titanium and a balance of iron.
 71. The airfoilaccording to claim 57, wherein said braze comprises between about 50 andabout 90 atomic percent titanium and a balance of nickel.
 72. Theairfoil according to claim 71, wherein said braze comprises betweenabout 71 and about 81 atomic percent titanium and a balance of nickel.73. The airfoil according to claim 56, wherein said braze comprisesbetween about 20 and about 85 atomic percent palladium with the balancecomprising one of chromium, aluminum, hafnium, zirconium, niobium, andvanadium.
 74. The airfoil according to claim 73, wherein said brazefurther comprises at least one additional element selected from thegroup consisting of silicon, germanium, hafnium, niobium, platinum,gold, aluminum, chromium, boron, zirconium, titanium, iron, nickel,cobalt, and vanadium, and wherein said at least one additional elementcomprises up to about 20 atomic percent of said braze.
 75. The airfoilaccording to claim 73, wherein said braze comprises between about 20 andabout 80 atomic percent palladium and a balance of chromium.
 76. Theairfoil according to claim 75, wherein said braze comprises betweenabout 39 and about 49 atomic percent palladium and a balance ofchromium.
 77. The airfoil according to claim 73, wherein said brazecomprises between about 70 and about 86 atomic percent palladium and abalance of aluminum.
 78. The airfoil according to claim 77, wherein saidbraze comprises between about 75 and about 81 atomic percent palladiumand a balance of aluminum.
 79. The airfoil according to claim 73,wherein said braze comprises between about 22 and about 32 atomicpercent palladium and a balance of hafnium.
 80. The airfoil according toclaim 79, wherein said braze comprises between about 25 and about 29atomic percent palladium and a balance of hafnium.
 81. The airfoilaccording to claim 73, wherein said braze comprises between about 10 andabout 35 atomic percent palladium and a balance of zirconium.
 82. Theairfoil according to claim 81, wherein said braze comprises betweenabout 22 and about 28 atomic percent palladium and a balance ofzirconium.
 83. The airfoil according to claim 73, wherein said brazecomprises between about 35 and about 60 atomic percent palladium and abalance of niobium.
 84. The airfoil according to claim 83, wherein saidbraze comprises between about 45 and about 49 atomic percent palladiumand a balance of niobium.
 85. The airfoil according to claim 73, whereinsaid braze comprises between about 20 and about 60 atomic percentpalladium and a balance of vanadium.
 86. The airfoil according to claim85, wherein said braze comprises between about 36 and about 44 atomicpercent palladium and a balance of vanadium.
 87. The airfoil accordingto claim 56, wherein said braze comprises between about 45 and about 90atomic percent zirconium with the balance comprising one of platinum andvanadium.
 88. The airfoil according to claim 87, wherein said brazefurther comprises at least one additional element selected from thegroup consisting of silicon, germanium, hafnium, niobium, platinum,palladium, gold, aluminum, chromium, boron, titanium, iron, nickel,cobalt, and vanadium, and wherein said at least one additional elementcomprises up to 20 atomic percent of said braze.
 89. The airfoilaccording to claim 87, wherein said braze comprises between about 68 andabout 90 atomic percent zirconium and a balance of platinum.
 90. Theairfoil according to claim 89, wherein said braze comprises betweenabout 77 and about 81 atomic percent zirconium and a balance ofplatinum.
 91. The airfoil according to claim 87, wherein said brazecomprises between about 45 and about 65 atomic percent zirconium and abalance of vanadium.
 92. The airfoil according to claim 91, wherein saidbraze comprises between about 55 and about 59 atomic percent zirconiumand a balance of vanadium.
 93. The airfoil according to claim 56,wherein said braze comprises between about 15 and about 80 atomicpercent niobium with the balance comprising one of iron, nickel, andcobalt.
 94. The airfoil according to claim 93, wherein said brazefurther comprises at least one additional element selected from thegroup consisting of silicon, germanium, hafnium, palladium, platinum,gold, aluminum, chromium, boron, titanium, iron, nickel, cobalt, andvanadium, and wherein said at least one additional element comprises upto about 20 atomic percent of said braze.
 95. The airfoil according toclaim 93, wherein said braze comprises between about 50 and about 80atomic percent niobium and a balance of iron.
 96. The airfoil accordingto claim 95, wherein said braze comprises between about 62 and about 66atomic percent niobium and a balance of iron.
 97. The airfoil accordingto claim 93, wherein said braze comprises between about 15 and about 50atomic percent niobium and a balance of nickel.
 98. The airfoilaccording to claim 97, wherein said braze comprises between about 35 andabout 45 atomic percent niobium and a balance of nickel.
 99. The airfoilaccording to claim 93, wherein said braze comprises between about 50 andabout 71 atomic percent niobium and a balance of cobalt.
 100. Theairfoil according to claim 99, wherein said braze comprises betweenabout 59 and about 63 atomic percent niobium and a balance of cobalt.101. The airfoil according to claim 56, wherein said braze comprisesbetween about 54 and about 74 atomic percent hafnium with the balancecomprising iron.
 102. The airfoil according to claim 101, wherein saidbraze further comprises at least one additional element selected fromthe group consisting of palladium, gold, aluminum, niobium, chromium,cobalt, nickel, boron, and vanadium, and wherein said at least oneadditional element comprises up to about 20 atomic percent of saidbraze.
 103. The airfoil according to claim 101, wherein said brazecomprises between about 62 and about 64 atomic percent hafnium with thebalance comprising iron.
 104. The airfoil according to claim 56, whereinsaid airfoil is a double-walled airfoil.
 105. The airfoil according toclaim 56, wherein said airfoil is located in a hot gas path of a turbineassembly.
 106. The airfoil according to claim 56, wherein said meltingtemperature is at least about 1700° C.
 107. The airfoil according toclaim 56, wherein said first piece comprises said first niobium-basedrefractory metal intermetallic composite.
 108. The airfoil according toclaim 107, wherein said second piece comprises said second niobium-basedrefractory metal intermetallic composite.
 109. The airfoil according toclaim 56, wherein said first piece comprises said first molybdenum-basedrefractory metal intermetallic composite.
 110. The airfoil according toclaim 109, wherein said second piece comprises said secondmolybdenum-based refractory metal intermetallic composite.
 111. Aturbine assembly having at least one component, said at least onecomponent having a melting temperature of at least about 1500° C. andcomprising: a) a first piece comprising one of a first niobium-basedrefractory metal intermetallic composite and a first molybdenum-basedrefractory metal intermetallic composite, wherein said firstniobium-based refractory metal intermetallic composite comprisestitanium, hafnium, silicon, chromium, and niobium, and said firstmolybdenum-based refractory metal intermetallic composite comprisesmolybdenum, silicon, and at least one of chromium and boron; and b) asecond piece joined by a braze to said first piece, said second piececomprising one of a second niobium-based refractory metal intermetalliccomposite and a second molybdenum-based refractory metal intermetalliccomposite, wherein said second niobium-based refractory metalintermetallic composite comprises titanium, hafnium, silicon, chromium,and niobium, and said second molybdenum-based refractory metalintermetallic composite comprises molybdenum, silicon, and at least oneof chromium and boron, and wherein said braze comprises a first metallicelement and a second metallic element, wherein said first metallicelement is one of titanium, palladium, zirconium, niobium, and hafnium,and wherein said second metallic element is one of titanium, palladium,zirconium, niobium, hafnium, aluminum, chromium, vanadium, platinum,gold, iron, nickel, and cobalt, wherein said first metallic element isdifferent from said second metallic element.
 112. The turbine assemblyaccording to claim 111, wherein said at least one component is one of anairfoil, a diffuser, a casing, and a seal ring structure.
 113. Theturbine assembly to claim 111, wherein said at least one component has aservice temperature of at least about 1000° C.
 114. A method of makingan article, the article having a melting temperature of at least about1500° C. and comprising a first piece and a second piece that are joinedtogether by a braze, wherein the first piece and second piece eachcomprise one of a niobium-based refractory metal intermetallic compositeand a molybdenum-based refractory metal intermetallic composite, whereinthe niobium-based refractory metal intermetallic composite comprisestitanium, hafnium, silicon, chromium, and niobium and themolybdenum-based refractory metal intermetallic composite comprisesmolybdenum, silicon, and at least one of chromium and boron, the methodcomprising the steps of: a) providing the first piece and the secondpiece such that the first piece and the second piece form an interfacetherebetween; b) providing a braze to the interface between the firstpiece and the second piece, the braze having a melting temperature andcomprising a first metallic element and a second metallic element, thefirst metallic element being one of titanium, palladium, zirconium,niobium, and hafnium, and the second metallic element being one oftitanium, palladium, zirconium, niobium, hafnium, aluminum, chromium,vanadium, platinum, gold, iron, nickel, and cobalt, wherein the firstmetallic element is different from the second metallic element; c)heating the first piece, the second piece, and the braze to a firsttemperature for a first predetermined hold time, the first temperaturebeing at least 20° C. above the melting temperature of the braze; and d)further heating the first piece, the second piece, and the braze to atemperature up to about 1450° C. for a second predetermined hold time,thereby joining the first piece and the second piece at the interfaceand forming the article.
 115. The method of claim 114, wherein the stepof providing a braze to the interface between the first piece and thesecond piece comprises providing a braze comprising between about 30 andabout 90 atomic percent titanium with the balance comprising one ofpalladium, platinum, gold, chromium, cobalt, nickel, and iron.
 116. Themethod of claim 115, wherein the braze further comprises at least oneadditional element selected from the group consisting of silicon,germanium, hafnium, niobium, palladium, platinum, gold, aluminum,chromium, boron, zirconium, iron, cobalt, nickel, and vanadium, andwherein the at least one additional element comprises up to about 20atomic percent of said braze.
 117. The method of claim 114, wherein thestep of providing a braze to the interface between the first piece andthe second piece comprises providing a braze comprising between about 20and about 85 atomic percent palladium with the balance comprising one ofchromium, aluminum, hafnium, zirconium, niobium, and vanadium.
 118. Themethod of claim 117, wherein the braze further comprises at least oneadditional element selected from the group consisting of silicon,germanium, hafnium, niobium, platinum, gold, aluminum, chromium, boron,zirconium, titanium, and vanadium, and wherein the at least oneadditional element comprises up to about 20 atomic percent of saidbraze.
 119. The method of claim 114, wherein the step of providing abraze to the interface between the first piece and the second piececomprises providing a braze comprising between about 45 and about 90atomic percent zirconium with the balance comprising one of platinum andvanadium.
 120. The method of claim 119, wherein the braze furthercomprises at least one additional element selected from the groupconsisting of silicon, germanium, hafnium, niobium, platinum, palladium,gold, aluminum, chromium, boron, titanium, nickel, iron, cobalt, andvanadium, and wherein the at least one additional element comprises upto about 20 atomic percent of said braze.
 121. The method of claim 114,wherein the step of providing a braze to the interface between the firstpiece and the second piece comprises providing a braze comprisingbetween about 15 and about 80 atomic percent niobium with the balancecomprising one of iron, nickel, and cobalt.
 122. The method of claim121, wherein the braze further comprises at least one additional elementselected from the group consisting of silicon, germanium, hafnium,palladium, platinum, gold, aluminum, chromium, boron, titanium, iron,cobalt, nickel, and vanadium, and wherein the at least one additionalelement comprises up to about 20 atomic percent of said braze.
 123. Themethod of claim 114, wherein the step of providing a braze to theinterface between the first piece and the second piece comprisesproviding a braze comprising between about 15 and about 80 atomicpercent hafnium with the balance comprising iron.
 124. The method ofclaim 123, wherein the braze further comprises at least one additionalelement selected from the group consisting of palladium, gold, aluminum,niobium, chromium, cobalt, nickel, boron, and vanadium, and wherein theat least one additional element comprises up to about 20 atomic percentof said braze.
 125. The method of claim 114, wherein the article is oneof an airfoil, a diffuser, a casing, and a seal ring structure.
 126. Themethod of claim 125, wherein the airfoil is a double-walled airfoil.127. The method of claim 114, wherein the article has a meltingtemperature of at least about 1700° C.